Painted it directly on to the cloth. It would have been prettier with gesso (and, I suppose, more authenic) but it's simply not worth the fuss as it will probably barely last one jousting season. The impact of the lances is going to ruin the paint and, eventually, will damage the cloth as well (and in a worst case ferrule hit scenario, damage the wood as well) so we'll just redo the layer of cloth and the painting for next year's jousting season.

I see what you are saying, the thing about the gesso, authenticity aside, is that it adds another layer to the shield, plus is easier to replace than the cloth, you simply soak it off, or scrape and re-coat add patches etc, it does allow for some nice raised work. In your case, I would simply have made up a new shield, after all the work is in the painting at the end of the day, the shield being the cheaper item when prep time is considered.